import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

class MyStack {
    Queue<Integer> qu1;
    Queue<Integer> qu2;
    public MyStack() {
        qu1=new LinkedList<>();
        qu2=new LinkedList<>();
    }

    public void push(int x) {
        if(!qu1.isEmpty()){
            qu1.offer(x);
        }else if(!qu2.isEmpty()){
            qu2.offer(x);
        }else{
            qu1.offer(x);
        }
    }

    public int pop() {
        if(!qu1.isEmpty()){
            int size=qu1.size();
            for(int i=0;i<size-1;i++){
                qu2.offer(qu1.poll());
            }
            return qu1.poll();
        }else{
            int size=qu2.size();
            for(int i=0;i<size-1;i++){
                qu1.offer(qu2.poll());
            }
            return qu2.poll();
        }
    }

    public int top() {
        if(!qu1.isEmpty()){
            int size=qu1.size();
            for(int i=0;i<size-1;i++){
                qu2.offer(qu1.poll());
            }
            int tmp=qu1.poll();
            qu2.offer(tmp);
            return tmp;
        }else{
            int size=qu2.size();
            for(int i=0;i<size-1;i++){
                qu1.offer(qu2.poll());
            }
            int tmp=qu2.poll();
            qu1.offer(tmp);
            return tmp;
        }
    }

    public boolean empty() {
        if(qu1.isEmpty()&&qu2.isEmpty()){
            return true;
        }
        return false;
    }

}